Consistently, the percentage of ATIIs expressing pRb, another hallmark of cell cycle progression, among adenomas and non-tumor alveolar areas from both BRAFV600E and control mice was not affected (Fig. 4B), therefore enforcing the evidence that acute BRAFV600E activation does not result in drastic changes in the expression of proliferative markers in ATIIs. This evidence concerns the gene RB1 and neoplasm.